1. Field of the Invention
This invention relates to systems for invasive medical procedures. More particularly, this invention relates to using magnetic fields to track a medical instrument within a living body.
2. Description of the Related Art
Magnetic tracking systems for medical application use magnetic fields to detect locations both of points in the patient's body and of invasive devices, such as catheters and surgical tools, that are in proximity to or inside the body. For this purpose, a magnetic field generator produces a field in and around an area of the body, and sensors in the body and in the invasive device detect the field. A system console receives the sensor signals and displays the location of the invasive device relative to the body.
For example, commonly assigned U.S. Pat. No. 7,174,201, issued to Govari, et al., and which is herein incorporated by reference, discloses apparatus for performing a medical procedure within a subject, which includes a wireless tag fixed to the tissue and which includes a first sensor coil. A second sensor coil is fixed to a medical device for use in performing the procedure. An integral processing and display unit includes a plurality of radiator coils, along with processing circuitry and a display. The radiator coils generate electromagnetic fields in a vicinity of the tissue, thereby causing currents to flow in the sensor coils. The processing circuitry processes the currents to determine coordinates of the tag relative to the medical device. The display is driven by the processing circuitry so as to present a visual indication to an operator of the medical device of an orientation of the device relative to the tag.
U.S. Pat. No. 5,913,820, issued to Bladen, et al., and which is herein incorporated by reference, discloses methods and apparatus for locating the position, preferably in three dimensions, of a sensor by generating magnetic fields, which are detected at the sensor. The magnetic fields are generated from a plurality of locations and, in one embodiment of the invention, enable both the orientation and location of a single coil sensor to be determined. The system allows an operator to wear small, single coil sensors about his body to enable his movements to be detected and interpreted by a machine without requiring physical contact between the operator and the machine. For example, the positioning system could enable an operator to interact with images on a television or computer screen without the use of a conventional keyboard, mouse or stylus.
U.S. Pat. No. 6,129,668, issued to Haynor et al., and which is herein incorporated by reference, discloses a device to detect the location of a magnet coupled to an indwelling medical device within a patient using three or more sets of magnetic sensors each having sensor elements arranged in a known fashion. Each sensor element senses the magnetic field strength generated by the magnet and provides data indicative of the direction of the magnet in a three-dimensional space.
U.S. Pat. No. 6,427,079, issued to Schneider, et al., and which is herein incorporated by reference, discloses a remote location determination system that uses splines of magnetic field values to determine location parameters. The location determination system is used on a laser catheter that is operable to perform myocardial revascularization. An automatic calibration technique compensates for any variations in gain in a sensor and related components. Methods for reducing the effects of eddy currents in surrounding conductive objects are used in electromagnetic position and orientation measurement systems.